Soil Microbial Community Characteristics Research Articles

Soil microbial community characteristics under different vegetation types at the national nature reserve of Xiaolongshan Mountains, Northwest China

Microorganisms provide ecosystem services, such as decomposition and mineralization processes in forest soils. Quercus aliena var. acuteserrata and Larix kaempferi are the main natural forest and planted forest, respectively, in the national nature reserve of the Xiaolongshan Mountains of China. Understanding the composition and structure of soil microbial communities under these two typical vegetation types is critical for achieving effective management and sustainable utilization of the forest vegetation in the Xiaolongshan Mountain region. In this study, we analysed and compared the soil microbial communities of the Q. acuteserrata natural forest and L. kaempferi planted forest using high-throughput sequencing technology, and cultivated land soil samples were selected as controls. The results indicated that soil nutrient contents and stoichiometric ratios (organic carbon to total nitrogen ratio (C:N), organic carbon to total phosphorus ratio (C:P) and nitrogen to phosphorus ratio (N:P)) were higher in the natural forest than in the planted forest and were lowest in the cultivated land. The soil bacterial community in the Q. acuteserrata natural forest had lower diversity indices than that in the L. kaempferi planted forest and cultivated land, and the soil fungal community in the Q. acuteserrata natural forest had higher diversity indices than that in the cultivated land. Proteobacteria was more abundant in the natural forest soil with higher nutrient levels, and Acidobacteria was more abundant in the plantation forest soil with lower nutrient levels. Ascomycota abundance was lowest in the natural forest, and Basidiomycota abundance was lowest in the plantation forest. Microbial composition was sensitive to soil nutrients and the stoichiometric ratio, which explained 82.67% and 70.72% of the total variations in the soil bacterial and fungal community composition, respectively. There were significant differences in soil microbial community composition and structure between the natural forest and planted forest, and these changes were influenced by soil nutrient conditions. Total phosphorus (TP) may be an important factor regulating microbial community structure in different vegetation soil types.

Effects of Phthalate Esters on Ipomoea aquatica Forsk. Seedlings and the Soil Microbial Community Structure under Different Soil Conditions.

Phthalate acid esters (PAEs) are the most frequently utilized synthetic chemical compounds worldwide. They are typical emergent contaminants and are currently attracting considerable concern due to their risks to plants, animals, and public health. Determining the vital environmental factors that affect the toxicity of target pollutants in soil is important for vegetable production and the maintenance and control of soil productivity. We investigated the influence of di-n-butyl phthalate (DBP) and bis(2-ethylhexyl) phthalate (DEHP) under different soil conditions on physiological changes in water spinach (Ipomoea aquatic Forsk.) seedlings and the rhizosphere soil microbial community. Supported by our former experiments in which we determined the representative concentrations that caused the most pronounced toxic effects, three experimental concentrations were studied including control soils without PAEs and spiked soils with either 20 mg DBP or DEHP kg−1 soil. The soil at all the three PAE concentrations was then adjusted to test two soil pH values, three levels of soil organic matter (SOM) content, and three levels of soil moisture content; thus, we completed 12 treatments or conditions simulating different soil environment conditions in greenhouses. After 30 days of cultivation, we analyzed the toxicity effects of two target PAEs on plant growth and physiological factors, and on soil microbial community characteristics. The toxicity of soil DBP and DEHP to the physiology of water spinach was found to be most affected by the soil pH value, then by SOM content, and least of all by soil moisture. The results of the 454 high-throughput sequencing analysis of the soil microbial community indicated that the toxicity of target PAEs to soil microorganisms was most affected by SOM content and then by soil moisture, and no clear relationship was found with soil pH. Under different soil conditions, declines in leaf biomass, chlorophyll a content, and carotenoid content—as well as increases in free amino acid (FAA) content, superoxide anion free radical activity, and hydroxyl radical activity—occurred in response to DBP or DEHP. Heavy use of chemical fertilizer, organic fertilizer, and high humidity led to the special environmental conditions of greenhouse soil, constituting the main conditions considered in this study. The results indicate that under the special highly intensive production systems of greenhouses, soil conditions may directly influence the effects of pollutant phytotoxicity and may thus endanger the yield, nutrient content, and food safety of vegetables. The combined studies of the impacts on plants and rhizosphere microorganisms give a more detailed picture of the toxic effects of the pollutants under different soil conditions.

Comparison of soil bacterial community and functional characteristics following afforestation in the semi-arid areas.

Changes in soil bacterial communities, which are crucial for the assessment of ecological restoration in Chinese plantations, have never been studied in the “Three North Shelterbelt” project in the semi-arid areas. We used high-throughput sequencing of the 16S rDNA gene to investigate the soil bacterial community diversity, structure, and functional characteristics in three plantation forests, including Populus × canadensis Moench (PC), Pinus sylvestris var. mongolica (PS), and Pinus tabuliformis (PT). In addition, soil environment factors were measured. There were distinct differences in soil characteristics among different plantation forests. Compared to PS and PT, PC had a higher soil pH, dissolved organic carbon (DOC), and available P, as well as a lower C/N ratio. Furthermore, afforestation with different tree species significantly altered the abundance of Proteobacteria, and Chloroflexi in the soil, and its influence on the bacterial diversity indices. The bacterial community compositions and functional groups related to C and N cycling from PS, and PT were grouped tightly, indicating that the soil bacterial phylogenetic distance of PS and PT were closer than that between PS plus PT and PC. Our results implied that the soil characteristics, as well as the diversity, compositions and functions related to C and N cycling of soil bacterial community obviously differed from the following afforestation, especially between PC and PS plus PT, which in turn enormously established the correlation between the soil microbial community characteristics and the afforestation tree species.

Soil microbial community characteristics in degraded karst tiankeng invaded by Eupatorium adenophorum.

After invading the grand negative landform karst degraded tiankeng, Eupatorium adenophorum will affect the plant diversity, community succession and natural ecological restoration of degraded tiankeng by changing soil microbial community. Taking the degraded tiankeng "Bajiaxiantang" as the research area, the soil around E. adenophorum roots in different habitats was selected to explore the microbial community characteristics of E. adenophorum roots using the Biolog-ECO micro-plate method. The results showed that the invasion degree of E. adenophorum was in order of pit slope shrub-grassland > pit bottom grassland > pit slope forest > pit head shrub-grassland. The characteristics of E. adenophorum varied among different habitats due to habitat heterogeneity. The change of microbial community metabolic activity, dominance index, richness index and evenness index of E. adenophorum roots was closely related with the invasion degree, with significant diffe-rence between inside and outside of the tiankeng. Amino acids and polymers were the main carbon sources utilized by soil microorganism. The α diversity of herbaceous plants in different habitats were correlated with that of soil microbial community. The diversity of soil microbial community around E. adenophorum roots increased significantly with the increases of invasion level, which could form a microenvironment conducive to invasion and colonization. In the future, the degraded tiankeng would eventually form the climax community of underground forests with community succession and natural ecological restoration, which might result in the disappearance of E. adenophorum in the degraded tiankeng.

Analysis of spatiotemporal variations in the characteristics of soil microbial communities in Castanopsis fargesii forests

Castanopsis fargesii is a good afforestation plants and various microorganisms play important roles in mediating the growth and ecological functions of this species. In this study, we evaluated changes in microbial communities in soil samples from C. fargesii forests. The phospholipid fatty acid (PLFA) biomarker method was used to obtain bacteria, fungi, actinomycetes, gram-positive bacteria (G+), gram-negative bacteria (G−), aerobic bacteria, and anaerobic bacteria to investigate spatiotemporal changes in microbial communities during the growing season. The results show that soil microorganisms were mainly concentrated in the upper 20-cm layer, demonstrating an obvious surface aggregation (P < 0.05). Large amounts of litter and heavy rainfall during the early growing season resulted in the highest PLFA contents for various microorganisms, whereas relatively low and stable levels were observed during other times. The dominant species during each period were bacteria. G+ or aerobic bacteria were the main bacterial populations, providing insights into the overall trends of soil bacterial PLFA contents. Due to the relative accumulation of refractory substances during the later stages of litter decomposition, the effects of fungi increased significantly. Overall, our findings demonstrate that the main factors influencing microbial communities were litter, rainfall, and soil field capacity.

Nitrogen addition accelerates the nitrogen cycle in a young subtropical Cunninghamia lanceolata (Lamb.) plantation

The nitrogen (N) cycle is likely to accelerate under future climate change. Leaf δ 15 N enrichment factor is an indicator of N status in young Cunninghamia lanceolata (Lamb.) plantation ecosystems. Given that N dynamics across the plant-soil continuum respond more strongly to N addition during the dry season when N leaching is minimal, fertilization during this period represents an optimal strategy for improving soil fertility. The effects of N deposition on N dynamics across the plant–soil continuum in subtropical regions are poorly understood. We investigated the effects of N addition on the N dynamics across the plant–soil continuum in young C. lanceolata plantations in different seasons as well as the effects of N addition on the soil microbial community. During the dry and wet seasons, we measured the concentrations of soil inorganic N, dissolved organic N in soil solution, leaf and root N concentrations, and stable isotope abundances, and soil microbial community characteristics. Short-term N addition decreased the levels of inorganic N, dissolved organic N, and leaf N concentration in the dry season; root N concentration was significantly higher in the high N and low N addition plots. Irrespective of treatment, the NH4+/NO3− ratio was higher in the wet season than in the dry season. The δ15N enrichment factors of the leaf and root in our experiments were closer to zero for all N addition treatments. Redundancy analysis revealed that the variation in the soil microbial community had low correlation with pH. Nitrogen dynamics across the plant–soil continuum respond more strongly to N addition in the dry season. High N deposition in N-saturated subtropical forest soil may rapidly increase leaching, particularly during the wet season. Nutrients in roots are more sensitive to changes in soil nutrient availability than those in leaves. The microbial community is primarily regulated by nutrient availability in the soil rather than by pH.

Above and belowground community strategies respond to different global change drivers

Environmental changes alter the diversity and structure of communities. By shifting the range of species traits that will be successful under new conditions, environmental drivers can also dramatically impact ecosystem functioning and resilience. Above and belowground communities jointly regulate whole-ecosystem processes and responses to change, yet they are frequently studied separately. To determine whether these communities respond similarly to environmental changes, we measured taxonomic and trait-based responses of plant and soil microbial communities to four years of experimental warming and nitrogen deposition in a temperate grassland. Plant diversity responded strongly to N addition, whereas soil microbial communities responded primarily to warming, likely via an associated decrease in soil moisture. These above and belowground changes were associated with selection for more resource-conservative plant and microbe growth strategies, which reduced community functional diversity. Functional characteristics of plant and soil microbial communities were weakly correlated (P = 0.07) under control conditions, but not when above or belowground communities were altered by either global change driver. These results highlight the potential for global change drivers operating simultaneously to have asynchronous impacts on above and belowground components of ecosystems. Assessment of a single ecosystem component may therefore greatly underestimate the whole-system impact of global environmental changes.

Effects of enclosing on soil microbial community diversity and soil stoichiometric characteristics in a degraded alpine meadow

Enclosing is an effective rehabilitation measure for degraded pastures that mimics natural recovery of vegetation. To examine the interaction between biotic and abiotic in lightly degraded and enclosing grasslands is helpful for a clear understanding of the structure and function of grassland ecosystem. In this study, soil microbial community and soil stoichiometric characteristics in lightly degraded and 10-year enclosing alpine meadows were studied by high-throughput sequencing and Biolog-Eco methods. The results showed that compared with lightly degraded grassland, the concentration of soil NH4+-N in the enclosing grassland increased significantly, while total K (TK) dramatically decreased. There was no obvious variation in soil total organic carbon (TOC), total N (TN), total P (TP), NO3--N, available P (AP), available K (AK), microbial biomass C (MBC) and microbial biomass N (MBN). The soil microbial biomass C/N was significantly enhanced. The carbon metabolic capabilities of soil microbes in different soil layers of alpine mea-dow were obviously increased with the prolonged incubation time, but there was no significant difference between lightly degraded and enclosed meadows. The OTUs of soil bacteria was significantly higher than that of fungi in alpine meadow. The microbial similarity between lightly degraded and fencing grasslands was 27.0%-32.7%. Enclosing significantly increased the fungal relative richness of Ascomycota, Zygomycetes and Chytridiomycota, while simultaneously decreased the rela-tive abundance of Basidiomycetes. Compared with lightly degraded meadow, the bacterial relative richness of Acidobacteria significantly decreased in enclosing meadow. The community composition of soil fungi and bacteria greatly varied among different soil layers. There was significant difference of fungal community composition in the upper soils between lightly degraded and enclosed grassland. The soil bacterial community diversity was greatly affected by soil TN and AK, while the fungal community diversity was significantly affected by plant aboveground biomass. Soil AK produced great influence on soil microbial carbon source utilization capacity. Generally, long-term grazing exclosure had no significant effects on soil nutrients and soil microbial community diversity of lightly degraded grassland and thus would waste the pasture resources, whereas appropriate grazing could maintain the sustainable utilization of grassland.

不同坡向凋落物分解对土壤微生物群落的影响

PDF HTML阅读 XML下载 导出引用 引用提醒 不同坡向凋落物分解对土壤微生物群落的影响 DOI: 10.5846/stxb201805261161 作者: 作者单位: 贵州师范大学贵州省山地环境重点实验室,贵州师范大学贵州省山地环境重点实验室,贵州师范大学贵州省山地环境重点实验室,贵州师范大学贵州省山地环境重点实验室,贵州师范大学贵州省山地环境重点实验室,贵州师范大学贵州省山地环境重点实验室,贵州师范大学贵州省山地环境重点实验室 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金项目（41461072，41601249，41661045）；黔科合[2018]5609 Effect of itter decomposition on soil microbes on different slopes Author: Affiliation: Key Laboratory for Information System of Mountainous Areas and Protection of Ecological Environment of Guizhou Province,,,,,, Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:采用空间与时间序列并用的方法，对贵州茂兰喀斯特森林阳坡和阴坡凋落物的分解特征及土壤微生物进行1年的野外调查和测定，探讨凋落物分解规律及其对土壤微生物群落的影响。凋落物在分解1年后的质量损失率约为72%，在分解过程中的碳、磷元素表现为释放，氮元素表现出富集；土壤微生物各群落磷脂脂肪酸（PLFA）在分解过程中的平均含量表现为：细菌（149.8 nmol/g） > 放线菌（63.9 nmol/g） > 真菌（31.3 nmol/g），阳坡和阴坡的微生物总PLFA在180d（559.2 nmol/g）和360d（513.6 nmol/g）的含量显著高于分解前；随分解时间的增加，阳坡细菌特征磷脂脂肪酸18：1ω7c的含量增加最大，其次是cy19：0和真菌特征磷脂脂肪酸18：1ω9c，阴坡土壤微生物PLFA含量表现出减少的趋势，细菌特征脂肪酸18：1ω7c减少量最大，约9.42 nmol/g，其次是i15：0和真菌特征脂肪酸18：1ω9c，约减少4.29-4.86 nmol/g；凋落物养分释放特征与微生物群落间的Spearman相关分析表明，真菌群落与碳元素释放率呈显著正相关关系，细菌群落与凋落物碳、磷元素的释放呈极显著正相关关系，且阳坡凋落物分解对微生物群落的影响高于阴坡。坡向和凋落物养分释放量对喀斯特森林凋落物的分解及土壤微生物群落的影响较显著，特征磷脂脂肪酸18：1ω7c、cy19：0、i15：0和18：1ω9c对环境变化的响应较为敏感。 Abstract:In this study, spatial and temporal methods were used to conduct field survey sampling and laboratory analysis of litterfall decomposition and soil microbe characteristics in the adret and ubac slopes of the karst forest ecosystem in Maolan, Guizhou. To provide a scientific basis for the monitoring of nutrient cycling and dynamic equilibrium in forest ecosystems, we systematically investigated the characteristics of litter decomposition and soil microbial communities in different slopes, and revealed the relationship between litter decomposition properties and soil microbial communities. We found that the mass loss rate of the litter in the decomposition bag during the 1-year decomposition period was approximately 72%. During the litter decomposition process, the carbon element was released and the total nitrogen content of the litter showed a tendency for enrichment. The total phospholipid fatty acid (PLFA) content in the adret and ubac slopes during litter decomposition was highest at 180 and 360 days, with values of 559.2 and 513.6 nmol/g, respectively. The content of the soil microbial community was in the order of Bacteria (149.8 nmol/g) > Actinomycetes (63.9 nmol/g) > Fungi (31.3 nmol/g). In the adret slope the bacterial characteristics of 18:1ω7c increased mostly after 360-days decomposition, followed by cy19:0, and the characteristic fungal PLFA 18:1ω9c compared to before the decomposition. The PLFA content in the ubac slope showed a decreasing trend. After decomposition of 360-days, the bacterial characteristic fatty acid 18:1ω7c exhibited the greatest decrease of approximately 9.42 nmol/g, followed by i15:0 and the fungal characteristic fatty acid 18:1ω9c, together showing decreases of approximately 4.29-4.86 nmol/g compared to the decomposition of 90-days. Spearman analysis indicated that a positive correlation was found between the fungal community and the carbon release rate. Additionally, there was a significant positive correlation between the bacterial community and litter carbon and phosphorus release, and the effect of litter decomposition on the microbial community was greater in the adret than the ubac slope. Slope and litter nutrient release produced the most significant effects on litter decomposition and on the microbial community in the karst forest; moreover, the characteristic PLFAs 18:1ω7c, cy19:0, i15:0, and 18:1ω9c were observed to be the most sensitive to environmental changes. 参考文献 相似文献 引证文献

Variation in the Soil Microbial Community of Reclaimed Land over Different Reclamation Periods

Improvement of soil quality after land reclamation is a key concern in mining areas. However, the characteristics and internal mechanisms of variation of bacterial community structure over different reclamation periods are currently unclear. The recovery and evolution of soil microbial community structure are important indicators of the level of soil quality improvement of reclaimed soil. Therefore, this study investigated soil samples from coal gangue-filled land after reclamation periods of 1, 6, and 15 years. To accomplish this, 16S rRNA gene libraries were produced to determine the microbial community composition of the soils. In addition, various soil microbial community characteristics in the filled reclamation areas were compared with soil samples from areas unaffected by coal mining. The results showed the following: (1) The diversity and abundance of bacterial communities in reclaimed soils was slightly different from that of natural soils. However, the soil bacterial community structure was highly similar to natural soil after a 15-year reclamation period; therefore, the recovery of bacterial communities can be used as an indicator of the effects of rehabilitation. (2) Some soil physicochemical properties are significantly correlated with the main bacteria in the soil. (3) The dominant bacteria included members of the phyla Firmicutes and Proteobacteria, as well as members of the genera Bacillus, Enterococcus, and Lactococcus. Taken together, the results of this study indicated that the application of microbial remediation technology can be used to adjust the soil microbial community structure, improve soil quality, and shorten the soil recovery period.

Effects of intercropping Chinese milk vetch on functional characteristics of soil microbial community in rape rhizosphere

The application of green manure is facing serious problems in purple soil region of southwest China. With the aim to explore the potential application of green manure, we examined the functional characteristics of soil microbial community in a system of Chinese milk vetch intercropped with rape. The innovations are the application of Chinese milk vetch in dry land of the southwest China and the establishment of new planting pattern of rape by providing empirical data. Results showed that the intercropping with Chinese milk vetch decreased the carbon resource use efficiency of microbial community in rape rhizosphere, especially for the utilization of carbohydrates. At the same time, Shannon index, Simpson index, and richness were reduced, but evenness index was increased by intercropping. Those results from cluster analysis and principal component analysis suggest that the soil microbial community composition was significantly different between monocropping and intercropping. The carbohydrates, amino acids and carboxylic acids were the sensitive carbon sources for differentiating the changes of the microbial community induced by monocropping and intercropping. Intercropping Chinese milk vetch could decrease functional activity, change community composition, and reduce diversity of soil microbial community in rape rhizosphere.

氮磷添加对亚热带常绿阔叶林土壤微生物群落特征的影响

PDF HTML阅读 XML下载 导出引用 引用提醒 氮磷添加对亚热带常绿阔叶林土壤微生物群落特征的影响 DOI: 10.5846/stxb201611012225 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金项目（31370626，31070588）；国家“973”计划项目（2012CB416905） Effects of nitrogen and phosphorus addition on soil microbial community characteristics in a subtropical evergreen broadleaved forest Author: Affiliation: Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:为了探讨氮磷添加对土壤微生物特点的影响，选择安徽省池州仙寓山常绿阔叶老龄林，设定了4个水平的氮磷添加试验，即对照（CK，0 kg N/hm2）、低氮（LN，50 kg N/hm2）、高氮（HN，100 kg N/hm2）、高氮+磷（HN+P，100 kg N/hm2+50 kg P/hm2）。利用氯仿熏蒸法和Biolog微平板技术，分析不同水平氮磷添加对不同土层（0-10 cm、10-20 cm和20-30 cm）土壤微生物生物量C（MBC）、N（MBN）和微生物群落功能多样性的影响。结果表明：MBC、MBN随土层加深而降低，且差异性极显著，MBC与MBC/MBN比在氮磷添加后均表现出显著性差异；土壤微生物群落的代谢活性随土层加深而降低，HN与LN处理的土壤微生物活性最高；McIntosh、Shannon和Simpson多样性指数在不同土层和不同N、P添加水平上都存在差异，表层土壤微生物多样性指数差异性较为显著。土壤微生物对羧酸类、氨基酸类和碳水类碳源利用率最高；主成分分析显示不同土层的土壤微生物碳源利用上有明显的变化，表层土壤微生物碳源利用在不同N、P添加水平上有明显的空间变异性，其他土层分布较为集中，空间差异性主要表现在对碳水类与羧酸类碳源的利用上。土层与氮、磷添加剂量对土壤微生物生物量C、N及功能多样性都有显著影响，其中高氮处理对表层土壤微生物影响最大。 Abstract:To reveal the effects of nitrogen and phosphorus addition on soil microbial characteristics, an old-growth evergreen broadleaved forest in the Xianyu Mountains in Chizhou of the Anhui Province was selected. Four treatments of nitrogen and phosphorus addition were designed, including a control (CK, 0 kg N/hm2), low nitrogen (LN, 50 kg N/hm2), high nitrogen (HN, 100 kg N/hm2), and high nitrogen + phosphorus (HN + P, 100 kg N/hm2 + 50 kg P/hm2) treatments. Microbial biomass carbon (MBC), biomass nitrogen (MBN), and microbial community functional diversity for different soil layers (0-10 cm, 10-20 cm, and 20-30 cm) were analyzed using the methods of chloroform-fumigation and the Biolog system. The results showed that MBC and MBN decreased with soil depth, with significant differences among soil layers (P > 0.05). The MBC and MBC/MBN ratio changed significantly after N and P addition. The metabolic activity of the soil microbial community also declined with soil depth. Soil microbial activities were highest in the HN and LN treatments. McIntosh, Shannon, and Simpson diversity indices differed in different soil layers and at different dosages of N and P. Microbial diversity indices for the 0-10 cm soil layer were significantly different among treatments. Carbon source utilization by soil microbes was highest for carboxylic acids, amino acids, and carbohydrates. The results of principal component analysis showed that carbon source utilization was different among the soil layers. There was significant spatial variability in carbon source utilization in the upper 0-10 cm of soil under different N and P treatments, whereas it was relatively stable in other soil layers (10-30 cm). This spatial heterogeneity was mainly manifested in carbon source utilization of carbohydrates and carboxylic acid. In general, the soil layer and N and P treatments had significant impacts on MBC, MBN, and soil microbial functional diversity, with greatest impacts occurring on the surface soil with high N treatment. 参考文献 相似文献 引证文献

Effects of Bisphenol A on Characteristics of Paddy Soil Microbial Community Under Different Cultural Conditions

Bisphenol A (BPA) is widely known as a typical synthetic environmental hormone. Effects of BPA concentrations and aerations on soil microbial communities were rarely reported. This paper presented the studies on effects of various concentrations of BPA (0, 0.25 mg·kg-1, 0.50 mg·kg-1, 1.00 mg·kg-1, 2.00 mg·kg-1) and soil aertaiton (aerobic and anaerobic) on characteristics of paddy soil microbial communites by technology of qPCR (fluorescence quantitative PCR) and PCR-DGGE (polymerase chain reaction-denaturing gradient gel electrophoresis). The results lined out that: ① the microbial abundance index was significantly different among different BPA concentrations under the same condition of soil aeration (anaerobic or aerobic). However, the index of microbial evenness, Shannon-Wiener-diversity and evenness-indices were insignificantly different under these conditions. At a concentration of 0.50 mg·kg-1, the microbial abundance index reached a maximum value under anaerobic conditions; while under aerobic conditions the opposite result was found, the microbial abundance index dropped to a minimum value. ② The two-way analysis of variance (ANOVA) showed that: the concentration of BPA, soil aeration and their interaction significantly affected the abundance of bacteria, whereas the abundance of fungi was only affected by soil aeration. The study results showed that: the abundance index was a sensitive indicator for the variation of soil microbial diversity; it was a critical value for the change of soil microbial abundance when the BPA concentration was 0.50 mg·kg-1; as for the abundance of fungi, the response of bacteria abundance was more sensitive to BPA and soil aeration conditions.

Responses of soil N-fixing bacteria communities to invasive species over a gradient of simulated nitrogen deposition

Soil N-fixing bacteria (SNB) play an important role in the invasion by invasive plant species (IPS). Meanwhile, progressive increases in the level of anthropogenic N deposition can change both soil physicochemical properties and the ecological characteristics of soil microbial communities, with particular impact on SNB. This can impact the soil micro-ecological mechanisms of invasion. This study used new-generation high throughput sequencing technology to determine the effects of invasive plant species Amaranthus retroflexus L. on the structure and diversity of SNB communities over a gradient of simulated N deposition (SND). The study found that soil pH decreased but soil electrical conductivity increased under A. retroflexus invasion. The diversity and richness of SNB decreased under A. retroflexus invasion, due to the altered soil nutrient content mediated by the root exudates released from A. retroflexus, and/or the decreased soil pH triggered by the invasion of A. retroflexus. SND at low levels (2.5–25gNm−2yr−1) decreased soil pH but SND at high levels (50gNm−2yr−1) increased soil pH significantly via soil secondary salinization. Thus, atmospheric N deposition may exert soil acidification at levels of atmospheric N deposition below critical values but soil alkalization when the level of N exceeds a critical threshold. To a certain extent, SND can increase the species number and the richness of SNB. SND at high levels (50gNm−2yr−1) significantly increased the diversity of SNB but significantly decreased the dominance of SNB. Amaranthus retroflexus invasion with SND can decrease the species number, diversity, and richness of SNB and increase the dominance of SNB. The interaction of these effects can produce a neutralizing effect on the diversity and richness of SNB. Thus, the invasion of A. retroflexus may be reduced under SND as a result of the decreased diversity and richness of SNB.

Endophytic fungi and soil microbial community characteristics over different years of phytoremediation in a copper tailings dam of Shanxi, China

We conducted a survey of native grass species infected by endophytic fungi in a copper tailings dam over progressive years of phytoremediation. We investigated how endophytic fungi, soil microbial community structure and soil physiochemical properties and enzymatic activity varied in responses to heavy metal pollution over different stages of phytoremediation. endophyte infection frequency increased with years of phytoremediation. Rates of endophyte infection varied among different natural grass species in each sub-dam. Soil carbon content and soil enzymatic activity gradually increased through the years of phytoremediation. endophyte infection rates of Bothriochloa ischaemum and Festuca rubra were positively related to levels of cadmium (Cd) pollution levels, and fungal endophytes associated with Imperata cylindrical and Elymus dahuricus developed tolerance to lead (Pb). The structure and relative abundance of bacterial communities varied little over years of phytoremediation, but there was a pronounced variation in soil fungi types. Leotiomycetes were the dominant class of resident fungi during the initial phytoremediation period, but Pezizomycetes gradually became dominant as the phytoremediation period progressed. Fungal endophytes in native grasses as well as soil fungi and soil bacteria play different ecological roles during phytoremediation processes.

Impacts of biocontrol products on Rhizoctonia disease of potato and soil microbial communities, and their persistence in soil

Four commercial biocontrol formulations (Bacillus subtilis GB03, Burkholderia ambifaria type Wisconsin isolate J82, Trichoderma virens Gl-21, and Trichoderma harzianum strain T-22), a chemical seed treatment (thiophanate-methyl, mancozeb, and cymoxanil mixture, TMC), and a combination chemical/biological treatment, were compared with no-pathogen and pathogen-treated controls, and monitored in two field seasons in Maine for their effects on the development of Rhizoctonia disease of potato and soil microbial community characteristics. All treatments reduced the incidence and severity of stem canker (37–75% reduction) relative to the pathogen control over both years, with the best control provided by B. subtilis and the combination chemical/biological treatment (TMC/Bamb). Both bacterial treatments (B. subtilis and Bu. ambifaria) reduced severity of black scurf in both years, and T. virens reduced scurf in one year, with reductions of 11–20% relative to the pathogen control. Over both years, the B. subtilis, T. virens, and TMC/Bamb treatments increased total and marketable yield, and Bu. ambifaria increased marketable yield, by 11–15% relative to the pathogen control. Substantial populations of the added fungal agents, but not the bacteria, were detected in bulk soil at the end of the growing season. Biocontrol treatments also significantly (P < 0.05) affected soil microbial community characteristics, as assessed by single carbon source substrate utilization (SU) and whole soil fatty acid methyl ester (FAME) profiles. Bacterial biocontrol treatments generally resulted in higher microbial activity and substrate utilization. Some effects on soil microbial communities were also observed the following spring (1 yr after application). This research indicates that biocontrol treatments can assist in the control of Rhizoctonia disease of potato, persist in soil to some degree, and have significant effects on soil microbial communities long after application.

English

The effects of three years continuous application of different rates of bio-organic fertilizer (BOF) were evaluated on three kinds of the counts of soil microbes, microbial metabolic activity and disease index of Verticillium wilt through greenhouse pot experiments. The results showed that, the BOF not only reduced the occurrence of verticillium wilt in cotton and decreased the counts of V. dahliae, but also improved the number of fungi, bacteria, actinomycetes, and microbial activity. The number of V. dahliae reduced gradually and fungi, bacteria, actinomycetes and average well color development (AWCD) firstly increased and then decreased with increasing the amount of fertilization in different organic matter content of soil. The number of V. dahliae was significantly increased by three years of fertilization. It showed that application of bio-organic fertilizer only delays the growth in the number of pathogen in soil within a certain time. The numbers of bacteria, actinomycetes were increased and the number of fungi was slightly reduced with increase of fertilization period. Application of bio-organic fertilizer made AWCD significantly higher than no fertilization (CK). By cluster analysis and principal component analysis, the results showed that the classification similar to disease index of various treatments, and it coincided with the number of microorganisms and AWCD values. BOF not only can control and improve the metabolic characteristics of soil microbial communities, but also maintain a high soil biological activity.© 2016 Friends Science Publishers Keyword: BOF; BIOLOG; Cotton verticillium wilt; V. dahliae; Principal component analysis

Crop Rotation in Paddy Soil Exhibiting Crop Failure Following Replanting: Effect on Soil Chemical Properties, Soil Microbial Community and Growth Characteristics of 2-Year-Old Ginseng

Crop Rotation in Paddy Soil Exhibiting Crop Failure Following Replanting: Effect on Soil Chemical Properties, Soil Microbial Community and Growth Characteristics of 2-Year-Old Ginseng

Cumulative and residual effects of different potato cropping system management strategies on soilborne diseases and soil microbial communities over time

Soilborne potato diseases and soil microbial community characteristics were evaluated over 8 years in different potato cropping systems designed to address specific management goals of soil conservation, soil improvement and disease suppression. Results were compared to a standard rotation and non‐rotation control in field trials in Maine. Standard rotation consisted of barley underseeded with red clover, followed by potato (2‐year). Soil‐conserving system (SC) featured an additional year of forage grass and reduced tillage (3‐year, barley/timothy–timothy–potato). Soil‐improving system (SI) added yearly compost amendments to SC, and the disease‐suppressive system (DS) featured crops with known disease‐suppressive capability (3‐year, mustard/rapeseed–sudangrass/rye–potato). Systems were established in 2004, evaluated with and without irrigation, and actively managed until 2010, with potato also planted in 2011 and 2012 to examine residual effects. All rotations reduced soilborne diseases black scurf and common scab, and increased yield after one rotation cycle (3 years), but diseases increased overall after two rotation cycles. DS maintained lower soilborne disease levels than all other rotations, as well as high yields, throughout the study. Cropping system effects became more pronounced after multiple cycles. SI system and irrigation both resulted in higher yields, but also higher levels of soilborne disease. Cropping system and irrigation effects were significant even after systems were no longer maintained. Soil microbial community data showed significant changes associated with cropping system, and differences increased over time. Cropping system strategy had significant and lasting effects on soil microbiology and soilborne diseases, and can be used to effectively enhance potato production.

Characterization of Soil Bacterial Diversity in Relation to Irrigation Water: A Case Study in China

Use of wastewater for irrigation has become indispensable worldwide due to accelerating water scarcity, and it also carries a social dimension of poverty reduction in developing countries. However, the impacts of wastewater irrigation on soil properties are still insufficiently understood, especially with regard to change in soil microbial community characteristics. The present study presents an assessment of soil bacterial communities subjecting to different irrigation waters. We conducted soil sampling in farmlands irrigated with wastewater, river water and groundwater respectively in an arid region of China and performed a metagenomic survey of microbial populations using the prokaryotic 16S ribosomal RAN gene. It sheds new light on possible alteration of soil bacterial diversity due to irrigation water. It also reveals that the relative abundance of nitrifying bacteria is greater in soil irrigated with river water than soil irrigated with wastewater. The opposite is true for denitrifying bacteria. The findings serve as a call for further in-depth study to explore the long-term responses of soil microbial communities to irrigation waters for the sake of environmentally sound watershed management.